Telephone line measuring and test equipment is customarily equipped with the capability of asserting line conditioning stimuli and measurement tone signals onto the (tip and ring) portions of the line and observing the response of the line to the asserted conditions and signals in order to obtain a measurement of the signal conveying capability of the line. One of the measurements that is carried out is a capacitance measurement operation, in which a prescribed low frequency audio reference tone (e.g. 30 Hz) is asserted on the line and the phase delay of a response tone measured across the line, which is indicative of the capacitance of the line, is observed.
With the increasing use of microprocessor-based equipment of telephone signal processing applications, it is desirable to minimize the number of discrete (analog) components that have been conventionally employed for functions such as capacitance measurement, and to transfer the task to a digital environment, where extremely precise analysis may be conducted in accordance with a programmable signal processing mechanism.